Dummy brush for slip rings



Aug. 4, 1959 F. W. UHINK DUMMY BRUSH FOR SLIP RINGS Filed April 25, 1957 INVENTOR. F/Q/fDE/CH UH/A/Af United States Patent Ofiice 2,898,487 Fatented Aug. 4, 1959 DUMMY BRUSH FOR SLIP RINGS Friedrich W. Uhink, Hamburg, Germany, assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Application April 25, 1957, Serial No. 655,058

1 Claim. (Cl. 310--228) My invention relates to the use of a dummy brush which is positioned in front of a current carrying brush which cooperates with a slip ring surface.

The use of slip rings and collectors or brushes for completing an electrical circuit between a rotating device and a relatively stationary device is well known in the art and is applicable in devices such as motors, generators and electromagnetic clutches.

One of the most severe problems in the use of a slip ring and cooperating collector is that during rotation of the device having the slip ring attached thereto, there is the possibility that the brush may slightly jump from the surface of the slip ring to thereby draw a small arc. This small arc will damage the surface of the slip ring, whereby the next time this damaged area of the slip ring is brought into engagement with the collector, there will be another jump of the collector with respect to the slip ring so as to aggravate the initial damage. This process is cumulative and can eventually lead to destruction of the collector or brush, or the slip ring surface.

The principle of my invention is to provide a dummy brush or collector which is positioned in front of the current carrying collector with respect to movement relative to the slip ring. Thus the dummy brush will in effect smooth the surface of the slip ring prior to engagement of the slip ring surface by the energizable brush. Hence, if a small arc is formed between the energizable brush and the slip ring surface to cause a slight damage to the surface during the next rotation of the slip ring which Will bring the damaged surface back into engagement with the damaged brush, this damaged surface will first be smoothed or leveled by the dummy brush.

A further advantage of my novel invention is that the dummy brush will sweep away oil or moisture and other foreign particles prior to the time of engagement between any slip ring surface and the energizable brush. Hence the contact resistance between the energizable brush and the slip ring surface will be appreciably reduced. if desired, the dummy brush can be constructed substantially identically to the energizable brush and be angularly displaced from the energizable brush by any desired amount.

Furthermore, the dummy brush may form a cylinder within which the energizable brush is positioned. In either case, it is seen that the dummy brush will sweep any particular area of the slip ring surface prior to the engagement of that area and the energizable brush.

Accordingly, a primary object of my invention is to provide a novel collector-slip ring arrangement.

Another object of my invention is to provide a novel dummy collector or brush which will sweep the area of a slip ring surface prior to the engagement of that sur face by an energizable collector brush.

Another object of my invention is to provide a novel brush construction wherein damage to the surface of a slip ring is smoothed out prior to reengagement of that damaged area and the energizable brush.

Still another object of my invention is to provide a novel dummy brush for sweeping impurities away from the surface of a slip ring prior to the engagement of that surface by an energizable brush.

These and other objects of my invention will become apparent from the following description when taken in connection with the drawing in which the figure shows an electromagnetic clutch having an energizing winding which is energized through slip ring and brush members.

More specifically, the figure shows an electromagnetic clutch body 10 which is fastened to a shaft 12 and carries an energizing winding 14 therein. For the purposes of the instant application, it is only important to understand that the energizing winding 14 must be energized through a slip ring and collector arrangement since the clutch body ill) is rotatable.

Clearly, however, the winding 14 could be any rotatable current carrying member which is to be energized from a relatively stationary source of power. In the case of the drawing, energization of winding 14 is taken from a slip ring surface 16 which cooperates with an energizable brush or collector 13 which is supported from a brush housing 20, the brush housing 20 being supported from a stationary member 22.

The brush housing 20 and its brush or collector 18 is then energized from a power source schematically indicated as D.-C. source 24 (although the power source could be an A.-C. source), through the conductor 26 while the other end of battery 24 is connected to a second slip ring 28 which engages shaft 12. The shaft 12 is then internally connected to an opposite end of winding 14 schematically indicated as conductor 30 so that a complete current path is completed which includes battery 24/, brush 28, shaft 12, Winding portion 30, winding 14, slip ring 16 (which has the other end of winding 14 attached thereto), energizable brush l8, conductor 26, and back to battery 24.

As previously indicated, if during rotation of slip ring 16 the energizable brush 13 should leave the surface of slip ring 16, a small arc will be drawn, to thereby cause slight damage to the surface of the slip ring. When this damaged portion is once again brought around to the energizable brush 18, there will be another jump and further damage, this damage being cumulative and leading to possible disability of the slip ring and brush. Furthermore, oil or foreign particles that adhere to the slip ring 16 will be brought into engagement with the brush 318 to thereby increase contact resistance and further increase possibility of damage to the slip ring surface 16 and increase wear of the brush 1%.

In accordance with my novel invention, I provide a dummy brush 32 which is positioned in a dummy brush holder 34 supported from a second portion of stationary member 22. Dummy brush 32 lies in the same plane perpendicular to the axis of rotation of slip ring 16 as does energizable brush 18 so that the dummy brush 32 will sweep the surface of slip ring 16 prior to its engagement by energizable brush 18.

Therefore, any damaged portions of the surface of slip ring 16 will be smoothed or evened out by the dummy brush 32 and similarly the surface of slip ring 16 may be swept clean of oil or foreign particles prior to engagement of those areas which are swept by the energizable brush 1%.

Accordingly, my novel dummy brush 32 which is isolated from any electrical potentials operates to increase the life of slip ring 16 and energizable brush 1? and further improves the operation of these members by decreasing contact resistance and heat developed in the area of contact between slip ring 16 and energizable brush 18. That is to say, the dummy brush 32 will mechanically remove any deposits that are developed on slip ring 16 so that the slip ring surface is always smpoth.

It is to be noted that in the case of the drawings, I have shown my novel dummy brush as being positioned 180 away from the energizable brush 18. Clearly, however, any angular displacement between theenergizable brush 18 and the dummy brush 32,may be utilized.

Furthermore, it may be desirable to, utilize a plurality of dummy brushes.

Asanother embodiment of novel invention, it will be clear that the dummy brush could be constructed as a concentric cylinder which surrounds the energizable brush 18 so that both the dummy brush and the energizable brush aresupported from the same brush, housing.

Although I have disclosed preferred embodiments of my novel invention, many modifications and variations will now be obvious to those skilled in the art, and I prefer therefore to be limited, not by the specific disclosure herein, but only by the appended claim.

I claim:

In, atrotating body having a slip ring thereon engageable by a relatively stationary energizable brush, said A relatively stationary energizable brush having a power source connected'thereto; a dummy brush being posi tioned to engage at least the same surface of said slip ring as engaged by said energizable brush during rotation of said rotating body and said slip ring; said dummy brush being isolated from the potential of said energizable brush; said dummy brush and said energizable brush being positioned in a common plane perpendicular to the axis of'rotation of said slip ring; saiddummy brush being identical to said energizable brush, said, dummy brush being interchangeable with said energizable brush,

References Cited in the file of this patent.

UNITED STATES PATENTS 338,197 Snowberger Mart 16, 1886 889,450 Foreman June 2, 1908 1,262,198 Jacobson Apr. 9, 1918 2,439,114 Vacha Apr; 6, 1948 2,761,569 Iserman Sept. 4, 1956 

